The bulk density of a material is the ratio of the mass of this substance in a freshly poured state to its volume. This takes into account both the volume of the substance itself, and the volume of voids inside it and the volume between individual particles (for example, in coal). For obvious reasons, this kind of density is less than the true density, which excludes the above voids.
To determine the bulk density, tools such as scales, a ruler, the Standard Funnel device, a measuring vessel of a certain volume are used. The bulk density of a substance is determined for a material of a certain moisture content. If the sample does not meet the humidity standards, then it is moistened or, more often, dried.
When we determine what is the bulk density of sand, then the algorithm of actions should be as follows:
1. The measuring vessel is weighed and placed under the standard funnel (it has a shutter at the bottom).
2. Sand is poured into the funnel, after which the shutter opens so thatso that the sand pours into the measuring vessel at once, fills it and forms a hill on top.
3. Excess sand is “cut off” with a ruler by moving along the top of the measuring vessel.
4. The vessel with sand is weighed, the weight of the vessel itself is subtracted from the total mass.
5. The bulk density is calculated.
6. The experiment is repeated 2-3 times, after which the average value is calculated.
In addition to the density in the loose state, the density in the compacted version is measured. To do this, the sand in the vessel is somewhat compacted on a vibrating platform for 0.5-1 minutes. You can calculate the bulk density of cement using the same method.
In accordance with GOST10832-2009, sand of a certain type (expanded) is divided into certain grades according to bulk density - from M75 (density is 75 kg / m3) to M500 (density 400-500 kg / m3). To be classified as a particular grade, sand must have a certain thermal conductivity and compressive strength. For example, the thermal conductivity of the M75 brand at a temperature of 25 C + -5 C should be no more than 0.043 W / m x C. And the compressive strength for the M500 brand sand is defined as 0.6 MPa (not less). Sand of quartz type (material moisture content 5%) has a bulk density of 1500. For cement, this figure is about 1200 kg/m3 in the free-flowing state and about 1600 kg/m3 in the compacted state. Often, an average figure is used for calculations, which is equal to 1300 kg / cubic meter.
Why do you needbulk density? The fact is that this value is used in trade turnover, and not the true density (for example, if sand is sold in bags). Therefore, in order to translate prices per cubic meter into prices per ton, you just need to know what is the density of the material. In addition, volumetric or weight data may be required for the preparation of mortars, depending on the instructions.
All product information, including density, is applied to each package by stamping, stenciling or printing on the label. It contains information about the manufacturer, symbols, date of manufacture and batch number, the amount of substance in the package and the mark of conformity.
